1. Field of the Invention
The invention relates to hydrocarbon-free aqueous creams of organosilicon compounds, their preparation and their use.
2. Description of the Related Art
Organosilicon compounds have been used for many years for the impregnation of inorganic and organic building materials in order to protect them against penetration of water. These silanes/siloxanes are employed as such, as solutions in solvents or in the form of emulsions. Aqueous hydrophilic emulsions of solvent-free organosilicon compounds are prior art and can be regarded as a substitute of equivalent value for solvent-based systems.
DE-A-199 45 305 relates to an impregnation cream for the waterproofing of building materials, which consists of a water-in-oil emulsion of hydrophobicizing organosilicon compounds, a nonactive hydrocarbon component, water, emulsifer and, if desired, auxiliaries and additives. The creams are prepared by blending two intermediate products in the form of creams. Hydrocarbons include, in particular, aliphatic and/or dearomatized petroleum spirit hydrocarbons, petroleum spirit hydrocarbons having from 9 to 12 carbon atoms and small proportions of aromatics, isoparaffinic hydrocarbons having from 11 to 15 carbon atoms and mixtures thereof.
EP-B-0 819 665 describes the preparation and use of an aqueous cream having a nonfluid consistency which penetrates into the building material after application and can be applied to the surfaces to be impregnated by blade coating and spraying. The cream-like consistency is based on the high active ingredient content of from about 65 to 90% by weight in the emulsion.
DE-C-40 29 640 describes the preparation of an emulsion having a low viscosity and a lower active ingredient content than that described in EP-B-0 819 665, which can be applied by rolling, spraying or flooding. The use concentration of this type of emulsions is generally 5-10%.
The emulsions described are water-dilutable oil-in-water systems (O/W).
However, these water-dilutable systems have a critical disadvantage. The application is very strongly influenced by the weather. If it starts to rain after application, the impregnated material is washed off from the exterior wall or washed out of the region close to the surface of the wall.
This applies particularly in the case of building protection systems which have a cream-like consistency and are applied in correspondingly high thicknesses. Since immediate penetration of the surface does not occur in the case of such systems, the cream remains on the building material surface before it is finally absorbed, so that this layer can be washed off more or less completely by rain and can get into the ground, which is ecologically and economically undesirable. Such an occurrence requires a second application.
Building protection emulsions having a low active content and a correspondingly low viscosity are washed out of the surface by rain after application. It is precisely in the region close to the surface where the water-repellent active ingredient should be located that impregnation has to be carried out again after rain.
Dong Hwang et al, Journal of the Korean Ceramic Society, Volume 37, No. 8, pp. 760 to 767, 2000, describe the emulsification of silanes as waterproofing agents for concrete. It is stated here that emulsions of silanes which require use of O/W and W/O emulsifiers are stabilized with the aid of polyvinyl alcohol (PVA).